Chris:

I'm loading up for a long weekend, so I took a quick measure with
(non-metric) tape:

length  20 11/16"
depth  12 1/2"
thick   1 11/16" (including the upper lip)

If you want more precise measurements, email me and I'll do it
after I return Monday.

                                            Richard A. Jones
                                            Boulder, Colorado
                                            '81 Vanagon   Mr Bus
                                            '87 Westy Syncro   El Jefe